Glutamates

Glutamates are the salts and esters of glutamic acid, one of the twenty standard amino acids. In physiological conditions, glutamic acid largely exists as the anion glutamate. The term commonly refers to monosodium glutamate (MSG), a flavor enhancer used in many foods to impart umami, and to other glutamate salts such as disodium glutamate, calcium glutamate, and potassium glutamate. Glutamates contribute to the savory taste by activating umami receptors on the tongue.

Beyond taste, glutamate is a major excitatory neurotransmitter in the vertebrate central nervous system, mediating synaptic transmission and participating in learning and plasticity. Dietary glutamate is rapidly metabolized in the intestine and liver, and the brain typically receives little directly from the diet because of the blood–brain barrier and amino acid transport regulation.

Dietary glutamates occur naturally in many foods, including tomatoes, mushrooms, cheese, and meat, and are present in fermented sauces, hydrolyzed proteins, and flavorings. In foods they may be bound as amino acids or occur as free salts or esters.

Regulatory bodies generally regard MSG and related glutamates as safe at typical consumption levels. Some people report sensitivity to MSG, but controlled studies have not consistently demonstrated adverse reactions. Because glutamates provide sodium in the form of salts, they can contribute to daily sodium intake and are a consideration for those on sodium-restricted diets.